There is a need for portable environmental control dike installations in areas where the activities of man pose a threat to the environment. One such example are the many sites across North America, where oil, salt water, fuel or other corrosive chemicals are stored in large tanks. When one of these tanks ruptures, the contents are spewed forth with disastrous consequences to the environment. Companies which maintain such facilities undertake periodic maintenance and replacement of the tanks, and as a further precaution build a dike to confine any toxic substances which would be released should the tank rupture. Prior to the development of the present invention all dikes were of a permanent nature constructed in the form earthen berms, or concrete construction. The disadvantages of a permanent installation of this type are that they are costly, must be destroyed in order to access the site to replace storage tanks and form a permanent scar on the environment.
In order to achieve the desired object of having a portable environmental control dike system the present invention uses free standing concrete panels. It is well known in the art that the ability of concrete to sustain an impact is extremely limited. Prior to the present invention one skilled in the art would have been of the opinion that it would not be possible to have a dike system constructed of concrete panels which were free standing. In order to have free standing concrete panels which two fundamental problems must be solved, namely; the strength of the concrete panels and strength of the joints.
The closest prior art with respect to the concrete panels used in the present invention is Canadian Patent No. 235,398. This patent discloses a metal frame which encloses a concrete filler material. The metal frame has vertical reinforcing bars and an internal reinforcing mesh. Although this patent issued in 1923, concrete panels constructed in accordance with the teaching of this invention have never been used in dike construction, and would not suitable for such purpose without modification as concrete would pull away from the longitudinal edges of the frame resulting in leakage.
There are several prior dike systems which employ concrete panels, none of which are free standing. Utilizing a modified form of the concrete panels of Canadian Patent No. 235,398 taken in any permissible combination with these systems they are not capable of being adapted as free standing units to perform the task for which the present invention was designed.
Canadian Patent No. 787,097 entitled "pre-cast segment storage tank", discloses a liquid storage tank intended for an underground installation. The patent teaches that the pre-cast concrete segments should be assembled on a concrete slab. It also requires a plurality of support beams which are said to "interlock with the longitudinal side walls of the tank to positively stabilize and maintain the side walls in their parallel spaced-apart upright position". It is questionable whether this structure could be free standing in the absence of the soil support and the support beams. The pre-cast segment side panels are joined in tongue and groove engagement. This type of joint would not withstand the force if a 450 gallon tank full of toxic chemicals ruptured sending a torrent of fluids rushing against the joints of the side panels. This type of concrete construction is constructed on ground level would crack and leak as a consequence of the ground movement known as "frost heaving."
Canadian Patent No. 1,124,541 entitled "Multi-Purpose Precast concrete panels and methods of Constructing Concrete structures Employing the Same", discloses two methods of deploying concrete sections to form a dike. In the methods disclosed concrete is poured through openings in the base of the concrete panels to "integrate the bottoms of said groups (of panels) by a mass of concrete extending therebetween and through the bottom rectangular openings of said groups". Each group of panels is described as lying "against an adjacent earthen mass". The joints between the panels are described as being tongue and groove which are "aligned adjacent their uppermost or generally horizontal edges by means of one or more "U" shaped aligning and cinching bolts". Even with the cinching bolts the tongue and groove joints are not capable of withstanding the force which would be applied from a torrent of fluids from a ruptured tank.